As compared with a liquid crystal display (LCD), an organic light-emitting diode (OLED) display device has attracted more and more attentions due to its advantages such as self-luminance, rapid response, high brightness, wide viewing angle, being rich in colors, and being thin and light.
Currently, as a mainstream development trend of the OLED display device, a gate voltage of a driving transistor may be changed, so as to control a source-to-drain current, thereby to change the brightness. In this regard, the driving transistor of the OLED display device may be in an on state for a long period of time, i.e., a positive or negative voltage may always be applied to the gate electrode of the driving transistor. However, a threshold voltage Vth and mobility of a conventional thin film transistor (TFT) made of different materials may change in the presence of direct current (DC) bias (i.e., the positive voltage may change in a trend opposite to the negative voltage), so such phenomena as change in the grayscale brightness, uneven grayscale (caused by the change in the characteristics of different TFTs) may easily occur after an OLED display panel operates for a certain period of time. It is impossible for a conventional pixel driver circuit to reduce the change in the grayscale brightness due to the change in the characteristics of the driving TFT after it works for a long period of time.